Process of making paper pulp



WIL IAM H. iaAson, or LAUREL,

, No Drawing.

-' Patented Aug. 23, 1932 fumrso STATES. P EN terrier;

' or LAUREL, urssrssirrr, A COBPORA'IIQN or DEL ARE rnooiiss or MAKINGPAPEB. rum

7 My invention relates to'a processof making paper pulp, andparticularly to a process of making paper pulp of ligno cellulosematerial, by exploding same into a state of line subdivision andtreating such finely subdivided material with chemical reagents.

1n the usual practice of making chemical paper pulp from wood chips,which always vary more or less in. size, the smaller pieces and theouter surfaces of all the pieces-are liable to be overtreated by thechemicals, whereas the inner portions of the larger pieces arefrequently found incompletely digested. In the chip making a greatdealof the comminuted wood has to be discarded as sawdust and the like priorto chemical treatment because of being too finely subdivided to betreated with the digester size chips.

The chemical action is uneven from other ly closed and filled withresins and, other wastematerial, while in the sap wood the cells areactive and much more open. The diiference in age of the various treesfrom which the wood is takenis also a factor in causing unevenchemicalreaction with certain parts overdigested and others mcompletelydigested. I When wood is prepared for pulp making by grinding, thefibers are broken and torn and reduced in length and are not welladapted for the production of paper pulp from' which strong, tough papercanbe made.

According to the present invention in order to give the chemicals fullaccess tothe wood fibers and to provide enormously large sur faces forchemical attack, the wood or other ligno-cellulose material which is tobe made use of for the production of paper pulp, is

*Appllcatlon'flled May 21,

and whereby 1925. Serial No. 31,785.

mssrssrrrnAssrenonro Asom'rn conron rron, I

exploded by being forcibly expelled from a high pressure chamber withinwhich: the material'has been subjected to the, penetrating action of ahigh pressure gas, such as steam, the ligno-xcellulose material, .isreduced to very finely subdivided state, being in fact in largepartreducedto its component 'ultiinate fibers. lVithsuch treatment thereis practically no reduction of fiber length, the fibers beingpractically all of their full natural length, and theexploded;ligno-cellu1ose material islong fibered and well adaptedfor theproduction ofpaper pulp from which strong, tough paper can bemade.[Practi cally every bit of the wood is recovered as pulp, includingtheexcessively dense and hard portions, such as knots, k'nurls which arethoroughlyreduced to the fibrous stateand available for making pulp.

In Patent N 0. 1,578,609 granted March 1926, I have shown and describedapparatus for performing the explosion operation- The explosion ispreferably produced by high pressure steam which is, of course, at acor-f respondlngly high temperature. By leading the exploded wood andexhaust.. steam-into a digester or vessel in whichthe chemicals forpulpmaking are contained, substantially all the otherwise waste heat canibe"'absorbed by the chemical liquid. The heat made use of toobtain theexplosion can thus bepractically all conserved.

According to the preferred embodiment of the invention the wood,chippedinto pieces of about the size customarilymade-use ofinchemicaldigesters, is introduced into a high pressurechamberandsubjected to penetraand the like,

tion by high pressure steam. After the pres- 'sureis balanced within andwithout themate'ri-al to be exploded, an,orific e is opened and thecontents ofthe chamber discharged,

the wood disrupting'into astate of fine sub- A division as it passes theorifice. The pressure is preferably maintalnedwithin the chamber duringthe explosion discharge so as to secure substantially. uniform,subdivisionand disin- 5 tegration from the-first stages of the dischargeright up to the completion thereof;

The pressures made use of in the explosion operation are in excess of250# per'square 800 er square inch. 1 I Ifiia e-found that when the wood.used is of a uniform moisture content, des rably at inch. [As thepressures are higher this, morecomplete and better disintegration 1Sbtained; A very desirably hi h state of dis integration has been obtainewith steam at or below the fiber saturation point? of the wood-,zamost-desirable condition is produced for explosion.

I heat up to the high temperatures, and a a ing fiber it may ,dry thewood so 'ture content anddesirably at or'near the arently thepenetration of the steam into t e interior of thewood is much more rapidand com leteand explosion thereof can. done much quicker with wood ofsubstant ally'umform low moisture content.

To obtain special conditions in the resultbe desirable to preliminarilythat it is of uniform moisfiber saturation point. Predrying the woodenables the" exploding to. be done quickly and substantially avoidsdiscolored products, which may be produced when the wood is held toolongunder the highpressure steam. After the wood "isexploded and therebyreduced to fibrous" state it is placed intoa digester and Desirably,although-not necessarily, the exploded woodand exhaust steam isleddirect into "the digester containing the chemical lost, but is in largepart in somecases reduction of the steam is possible. There is morenearly the theoretical recovery of the complete cellulose content aspulp. 'A'more uniform product-is obtainable apparently because of thevery extensiveexposure of the lignin's and othernon-cellulose 1 as'is'required for ver high grade 'pulip, a by components to the action ofthechemical reagent. The pulp after digestion is ready for treatment in,a beater, Jordan'or thelike apparatus for the production of paper.

Instead ofdigestingthe fibers completely very-desirable class 0 pulp isobtaine only partiallyv digesting the exploded and exposed: fibers sothat the lignin is'removed to anzextent from the individual fibers andit ispossible to hydrate material so obtained .bythe-usual process'ofhydration, such as .beatinggordaning, etc. 1 1

Another mode of procedure in making pulp Less steam is required, on'ac'count apparently of there being less water to subjected to chemicaldiges- "-tion' either of the acid or alkaline type in order to digestand remove all or part of the, lignins and produce commercial celluloseI claim:

the diges- 1 ama sion treatment is to subject chips to complete acombination of chemical and exploorpartial chemicaltreatment prior toexplosion. Such treatment may be carried out in an enclosed chamber, thesurplus chemical removed as by draining it. out and then the chi smay besubjected in the chamber to very hig steam pressure, such as pressure.over"- 250# and preferably over-400.1; per square inch, "and ,rojected'from the container'as described a ove, so that the resulting fiber is hihly disintegrated. Many of the cellureadily and more or lesscompletelyhydrated by the ordinary beating; process, and made available for a goodgrade of paper. If desired, the pretreatment with a chemical may becarried out in a separate-vessel ordigester nor to the introduction intoand explosion:

rom the high pressure chamber. After exlose here have lost part or allof their coating of encrusting lignms so that they may be losion afurthersecond treatment in a chemical digester maybe resorted to, ifdesired.

The pretreatment with chemicals prior to explosion, when resorted to,may be of various kinds. F orexample, discoloration produced b somewhatprolonged exposure to extra high pressure steam appears to be due togeneration or liberation of acids, etc., and preliminary treatment withneutralizing chemicals can be resorted to with advantage, especiallywhen the steam pressures are extra high and discoloration of the productis undesirable. v I

ulp, which con- 1. The process of makin Q jecting subdivi e wood tochemsists in su icaltreatment in a chamber, removing surplus chemicals,subjecting the treated mate-'2 rial to steam pressures in excess of250#- r square inch in said chamber,-and discharging from said chamberat such pressure, whereby the material is exploded and thoroughlyd1sintegrated.

2. The process of makin pulp, which conical digestion in a chamber,removing sur plus chemicals, subjecting the treated mate jecting subdivied wood to chemrial to steam pressures in excess of 250%: per

square inch in said chamber, discharging said chamber at such pressure,whereby the material is exploded and thorou hly disinte rated, and subecting the pre igested an exploded material to further chemical 'diges a3. The rocess of makin pulp which consists in su jectingsubdivi edligno-cellulose I material to penetration by steam under pressure inexcess of 250 pounds per square inch in a closed chamber, progressivelydischarging the ligno-cellulose material and steam through a constrictedopening and leading the ex loded material and exhaust steam into aliquld containing a=chemical reagent-"for digesting, whereby the heat ofthe steam used for ex losion is absorbed in the chemical re agent ath.

4. The recess of making pulp, which consists in subdivision of wood intosubstantiall chip form, subjecting same to partial chemical digestion,draining off the surplus'liquid and exploding such pretreated wood intofibre b progressively discharging the same through a constricted openingfrom under pressure in excess of 250# pensquare inch. 5. The process ofmaking pulp, which consists in subdivision of wood into substantiallychip form, subjecting same to partial chemical digestion, drainingofithe surplus liquid, exploding such pretreated wood mto fibre bprogressively discharging the same throug a constricted opening fromunder pressure in excess of 250# per square inch, I and subjecting thepartially digested and exploded fibrous material to further chemicaldigestion. p

In testimony whereof, I have signed my name hereto.

- WILLIAM H. MASON.

